Minicircuits.com looks interesting, but their array of parts is bewildering. Lots of VCOs but I don't see a PLL to use as local oscillator.A few of thoughts:
If you have access to the audio consider feeding it to a transmitter at a more convenient frequency, that could be audio from the microphone/speaker on stage making a sort of repeater.
Another approach is to get a mixer and osciilator from a company like https://www.minicircuits.com/ and make an RF converter for a small commercial receiver. Broadcast FM uses wideband FM and communications channels use narrow band FM. A wide band receiver can be used to receive narrow band FM with loss of speaker amplitude. Doing it the other way around -a narrow band receive listening to a wide band signal would probably result in distortion.
A regenerative receiver can be used to demodulate FM and it would not take many parts, thought I wonder whether frequency stability would be a problem. It would definitely need to be inside a conductive container with a preamp to keep the receiver from having its frequency shifted by stray capacitance to the antenna.
You can buy cheap hearing aids in many parts of the world now, and maybe that would be the simplest solution.
I already wear hearing aids. I'm not sure how a transmitter at a more convenient frequency would be legal. Hacking a DECT phone might be a possibility except that info on the DECT modules they all use seems to be impossible to obtain.